This invention relates to component carriers. In particular it relates to component carriers adapted for mounting components on curved surfaces. One application where this invention is particularly useful is mounting transformers on curved circuit boards.
One method for constructing a transformer is to wind wire around an iron core. Another method is to wind the wire around the circumference of a doughnut shaped bobbin made of plastic acetal or like material and to then fasten an iron core in the center of the bobbin. Bobbin type transformers, also called modular transformers, are sometimes used for circuit board applications. Transformers used on circuit boards generally have very thin fragile winding leads.
Conventionally, bobbins for modular transformers have been integrally manufactured onto carriers. An advantage of mounting a transformer bobbin onto a carrier is that the fragile transformer winding leads can be affixed to the more sturdy carrier pins. In the prior art, such carriers are flat bottomed and are available for either surface mount or through-the-board mount applications. In some applications the carrier is designed to minimize component height by mounting flush to the circuit board.
Conventional transformer bobbins with integrally manufactured carriers are well suited for applications involving flat circuit boards. However, they are impractical to use on curved circuit boards, especially where it is critical to maintain the lowest possible component height. An example of such an application, requiring curved circuit boards and low component height is a toroidally shaped power supply that fits around a cylindrically shaped photo-multiplier tube.
In configurations where the circuit board is curved, a conventional modular transformer bobbin with flat bottom carrier will not mount flush to the board. Instead, only the opposed ends of the carrier base will abut the surface of the circuit board at points along the arc formed by the curved surface of the board. This causes the effective height of the transformer, measured from the surface of the circuit board to the point on the transformer furthest from the surface of the circuit board, to be greater than it would be if the same transformer were mounted on a flat circuit board. Moreover, conventional bobbin mounts cause excessive stress, particularly with relatively flexible circuit boards, at the points where the carrier intersects the surface of the board. Furthermore, conventional bobbin mounts also cause the carrier leads to be stressed as the circuit board is formed into its cylindrical shape.
One solution to this problem has been to mount transformer bobbins directly on the circuit boards, without carriers, for applications involving curved circuit boards where component height is critical. This approach, however, can be very costly. As mentioned above, the winding leads on unmounted transformers are very fragile and many are broken during testing. This causes considerable waste in both materials and labor. To avoid lead breakage, unmounted transformers are generally installed onto the circuit board and then tested in place. While this method avoids destroying transformers during testing, it also causes great waste. If a transformer proves to be defective after it is mounted to the circuit board, the entire circuit board must be discarded.
Accordingly, it is an object of the present invention to provide a rigid component carrier with a curved bottom adaptable for mounting components to concave curved surfaces.
It is a further objective to provide a carrier adaptable for use in applications involving curved circuit boards, particularly where component height is a critical factor.
Another object of this invention is to provide an improved carrier for supporting transformers on curved circuit boards in such a way that reduces the waste costs associated with testing those transformers.
Additionally, it is a object of this invention to eliminate both the problem of stressing the circuit board at the points where the bobbin carrier abuts the circuit board, and also the problem of stressing the carrier leads when the circuit board is formed into a cylindrical shape.